Background Both atmospheric particulate matter pollution and combined high-fat and highglucose diet are related to cognitive function and neurodegenerative diseases, but there are few reports on the synergistic effect of the two factors.
Objective The study is conducted to investigate the effects of atmospheric particulate matters and combined high-fat and high-glucose diet on the mRNA expressions of cAMP-response element binding protein (CREB), brain derived neurotrophic factor (BDNF), extracellular regulated protein kinases 1 (ERK1), and extracellular regulated protein kinases 2 (ERK2) in cerebral cortex and hippocampus in male rats.
Methods A total of 48 male SD rats aged three weeks were randomly divided into four groups:control group (normal feed, no atmospheric particulate matter exposure, CC group), high-fat and high-glucose diet group (high-fat and high-glucose feed, no atmospheric particulate matter exposure, HC group), atmospheric particulate matter exposure group (normal feed, atmospheric particulate matter exposure, CP group), and atmospheric particulate matter exposure plus high-fat and high-glucose diet group (high-fat and high-glucose feed, atmospheric particulate matter exposure, HP group). In independent ventilation cages, the rats in the CP and HP groups inhaled air containing atmospheric particulate matters, while the rats in the CC and HC groups inhaled air filtered by high efficiency filters (atmospheric particulate matters with aerodynamic diameter >0.1 μm were filtered out). Rats' cognitive function was measured by open field test after the three-month exposure. The mRNA expressions of CREB, BDNF, ERK1, and ERK2 in hippocampus and cerebral cortex were detected by RT-qPCR. One-way ANOVA was used for comparison between groups, and factorial ANOVA was used for interaction effects.
Results The average number of grid crossings of rats in the CP group was 46.60±16.55, and the total distance and the number of grid crossings of rats in the HP group were (163.17±32.54)m and 43.40±8.40, respectively, all lower than those in the CC group; the time spent in the central grid in the HP group(7.58±1.27) s was higher than that in CC group (Ps < 0.05). In cerebral cortex:the mRNA expression levels of CREB and ERK2 in the HC group, CREB and ERK2 in the CP group, as well as CREB, ERK1, ERK2, and BDNF in the HP group were all lower than those in the CC group (P < 0.05); the mRNA expression levels of CREB and BDNF in the HP group were lower than those in the HC group (P < 0.05); the mRNA expression levels of CREB, ERK1, and BDNF in the HP group were lower than those in the CP group (P < 0.05). In hippocampus:the mRNA expression levels of ERK2 in the HC group, CREB and ERK2 in the CP group, as well as the four genes in the HP group were all lower than those in the CC group (P < 0.05); the mRNA expression levels of the four genes in the HP group were lower than those in the HC group (P < 0.05); the mRNA expression levels of ERK1 and BDNF in the HP group were lower than those in the CP group (P < 0.05). The results of factorial ANOVA showed that there was no interaction between atmospheric particulate matter and combined highfat and high-glucose diet on the total distance, the number of grid crossings, the time spent in the central grid, and the mRNA expression levels of CREB in cerebral cortex and hippocampus in male rats (Ps> 0.05).
Conclusion Particulate matters at certain levels and combined high-fat and high-glucose diet may separately reduce the mRNA expressions of CREB, BDNF, ERK1, and ERK2 in cerebral cortex and hippocampus in male rats, but the synergistic effects of the two factor have not been observed.
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